Torkel easily leapt to the roof using a boost from his jet pack. As he landed he saw the alien he was after running across the roof, zig-zaging between ventilations fans. Torkel threw himself into cover and peeked out just long enough to spot the alien sitting pretty behind a vent. He fired a few shots off in the general direction to see if he could scare the extraterrestrial out, but it had no effect. 
Very carefully he started to sneak around to the side. If he could flank the alien and put a laserbeam through its head he could get back to his squad. Carefully, quietly, minding every step. He kept his body low, always a vent or chimney or something between himself and the alien. After almost a full minute of sneaking, while the rest of the team engaged the mutons, Torkel had arrived, flanking position, just a quick shot to the head and everything would be done.
He arranged himself behind the vent. Crouching low, but both feet on the ground, quick up-and-down.
He aimed down his sights and stood up as fast as he could, before he was half-standing he could see the vent that the alien used as cover and turned his rifle to aim at nothing.
It had moved, he swept the rifle left and right, trying to find the alien, as he turned to look behind he slammed the barrel of the rifle into the alien’s face. 
It yelled out in pain and jumped back, trying to get. Torkel got a good look at it this time. Huge claw-like legs, scary-looking… A chryssalid. Without a thought Torkel let loose a few more shots, but stunned and confused as he was, he could not confirm a hit. 

Now the hunt was on, the chryssalid was on its way back to the team, if Torkel could not catch the thing before it got off the roof the chryssalid could do some serious damage on the ground. He was just about to warn his team when a thick russian voice came from the other end. 
"Torkel, see if you can't get that bastard off the roof, and do it fast. I have a surprise for our friend."
Exactly what he needed. a pincer-maneuver. 
“I’ll send him to you within ten” Torkel replied and went into overdrive, his thighs flexing, sending his feet down with enough force to propel the tall man faster than most normal humans. The chryssalid had almost reached the edge of the roof but on the wrong side. A few shots at the place where the alien was planning to jump down changed its mind. It dropped into cover again, but Torkel could not wait. Another shot kept the alien pinned and drained the battery on his rifle. No time to reload. He left the rifle on the ground and pulled out his plasma gun. As he activated his jetpack he threw himself on the ground toward the alien. The booster dragged his body along the ground, and without the armor he’d be in a world of pain, but the guys down at R&D had done a fine job. Torkel could barely feel a thing. He only needed a second of boost and then cut it off, but his body kept going. while he flew across the roof, propelled now only by his own momentum, he turned around to get his feet first. 
When he slammed into the short wall that marked the end of the roof his legs along with servoes built into the armor took the whole load and kept his steady. 
There he was, lying on the ground, both feet against the low wall, both arms stretched out and both hands clutching the plasma gun aimed at the chryssalid. The alien wasn’t given a chance to react, the gun send green fire out towards it. 
The first one would’ve hit if the creature hadn’t turned around, the second hit it in the back and sent it stumbling forward. It saw the handles if a built-in ladder and barely a second later it was climbing down, away from the crazy humans with all the guns. Halfway down an explosion shook the building and made the whole wall crumble down, the chryssalid was trapped under several hundred pounds of bricks, shards of glas and metal. Bones broken, internal bleeding, external bleeding… It died only seconds later. After retrieving his rifle and swiftly reloading it Torkel jumped down and confirmed the kill.